1. Field of Invention
The present invention relates generally to the field of built-up roofing for buildings, and means for supporting such built-up roofing so as to permit the effective insulation of the building.
2. Discussion of the Prior Art
A large percentage of the buildings throughout the world use built-up roofs, which are built up from a deck which is in turn secured, generally by spot welding, to secondary structural members such as bar joists. A built-up roof generally comprises one or more waterproof membrane layers which are adhesively secured to a base support carried by the deck or, alternatively, are secured directly to the deck.
In prior art built-up roof constructions, insulation of the built-up roof has been accomplished by including one or more layers of insulation material in the layers of material stacked above the deck to form the built-up roof. Since insulation generally depends on the presence of gas pockets to reduce heat transfer, it tends to be light, compressible and of low structural strength. Inclusion of insulation layers in a built-up roof thus tends to reduce its strength, rendering it vulnerable to tears, punctures and damage from foot traffic and the like. While a more rigid insulation layer may be provided to reduce the incidence of these problems, such a rigid layer tends to be correspondingly less satisfactory from a heat transfer standpoint.